1. Field of the Invention
This invention relates to a key telephone system comprising a key station unit and a plurality of key telephone sets connected thereto, and more particularly to a key telephone system wherein various operating data stored in a memory device of the key station unit can be set or altered by using keys of at least one of specific key telephone sets among the plurality of telephone sets.
2. Description of the Prior Art
There has been a known key telephone system in which various operating data stored in a memory device of a key station unit are set or altered by using a key(s) of a specific key telephone set among a plurality of telephone sets. In such a telephone system, for setting the operating data, various data regarding specific operation items are assigned to respective keys of the specific telephone set so as to set respective data according to the operation of the keys. For example, when 20 keys each associated with a luminous display device using LED are provided and when it is desired to set the office lines through which calling can be made from the 10th key telephone set, the setting is made in the following manner.
At first, a number, for example 3, representing an operation item corresponding to the setting of an office line capable of calling from the specific key telephone set, is inputted by a dial key. Then, a number, 10, representing that the data setting is executed with respect to the 10th key telephone set, is inputted by the dial key. Under this condition, the LED display device associated with a key corresponding to an office line capable of calling is lighted, while the LED display devices corresponding to other keys are not lighted. In other words, the office line assigned to a key associated with a lighted LED display device is capable of calling, whereas office lines assigned to keys associated with extinguished LED display devices are incapable of calling. When a key associated with a lighted LED display device is depressed, the LED display device is turned OFF. On the other hand, when a key associated with an extinguished LED display device is depressed, the display device is turned ON. In this manner, by the operation of the keys, the setting is changed from the state capable of calling to the state incapable of calling, and vice versa.
When the fact that the necessary data has been set is confirmed by the LED display device, a key, for example, a holding key "HOLD" for inputting data representing the fact that the setting has been completed is depressed. Thus, the setting of operating data for an office line capable of calling from the 10th telephone set is completed.
In the above described example, according to the prior art key telephone system, a maximum of only 20 of the data setting is possible corresponding to 20 keys provided in the specific key telephone set.
In the key telephone system of this type, the number of keys that can be used for the data setting of each key telephone set, that is, the number of keys associated with respective LED display devices has decreased in recent years for the purpose of the cost down of the system and easiness of the operation, and due to the fact that the number of office lines utilized for respective telephone set is generally smaller than that of the office lines utilized in the entire system. As a result, it often becomes impossible to set all data by a key telephone set utilized for the data setting.